Desert Oak: an icon of inland Australia
Desert oaks in central Australia. (Photo by Jack Bradshaw)
The American naturalist and philosopher Henry David Thoreau once wrote a lovely line about the great white pine forests of Connecticut. The trees, he said, were “like great harps, on which the wind makes music”.
It is a line that comes to mind whenever I am camping among or resting on a hot day in the shade of a stand of sheoaks. To some people’s ears the sheoak sings a melancholy refrain, but to me it is perhaps the sweetest music of the bush.
And of all the sheoaks, is there a more beautiful (but at the same time more frustrating) tree than the desert oak? Nobody who has seen a clump of desert oaks in their natural habitat of spinifex plains, red sand dunes and rocky ranges will argue with my appreciation of their beauty, and nobody who has rested in their shade as a dry wind rustles their feathers, will forget the music they make.
This arises from my inability to grow the thing. Being a forester, I fancy myself as someone who can grow trees, but the desert oak (sometimes also called the ‘desert sheoak’, but still Casuarina decaisneana)has always defeated me. For a start you have to grow your own - I have never seen seedlings for sale in nurseries. I have many times collected seeds and have sown them on an ashbed or in pots in a commercial potting mix. I have also many times managed to germinate and raise some tiny seedlings and later carefully planted them out and cared for them. But never with success. Despite every precaution, including cultivation of the soil, shelter from wind and sun, controlling weeds, a sniff of fertiliser and mulch from other sheoaks, within days of being planted the seedlings curl up their toes and wither away.
And to increase my frustration, I know that other people can do it. There are some beauties shading the carpark at Uluru airport where once I had to kill a couple of hours between flights, and I have read (with envy) about Neville Bonney’s successfully planted groves in his arboretum near Palmer in South Australia.
A grove of desert oak saplings, shooting up like spears. Photo by Neville Bonney
Perhaps my tender-loving-care was too tender and too-loving; perhaps my soil at Gwambygine is too loamy - they naturally prefer well-drained sandy soils - or perhaps there is something special in the desert soils or the desert air where they grow naturally. Whatever is this secret ingredient, it does the job. In the remote and unforgiving environment of the outback, young desert oaks come away very happily in dense groves after a bushfire or a flood, with no-one to offer them a moment's loving care. The young trees shoot up like spears, and then eventually the crowns spread out when the deep roots find the water table.
[An aside: Hey! what about that name? The botanists among my readers will have already become restless at my mention, above, of desert oak’s scientific name, which I gave as Casuarina decaisneana. Allow me an indulgence. When I first knew them, Australian sheoaks, of which there are nearly eighty species, were all classified as members of the genus Casuarina. Then one day a Canberra botanist got into them, subdivided them up, and called some Casuarina and some Allocasuarina (botanical latin that means, I think, “rather like Casuraria”). The former have blackish-coloured seed and the latter, brownish-coloured seed. Desert oak was one of those renamed Allocasuarina. It is not compulsory to adopt a new botanical name like this, and I continue to call them all, including desert oak, Casuarina. I like the fact that this name is derived from “kasuari”, the Malay word for the cassowary, and is a reference to the similarity of the tree's drooping foliage to the drooping feathers of that wonderful bird of the Queensland rainforests].
Back to desert oak, and its drooping foliage …
The ability of the desert oak to prosper in the bush, but at the same time to reject my attempts at cultivation is another reason I love them – they seem almost to have a proud independence, and to say in response to my proffered hand “No thanks, I can look after myself”.
And look after themselves they do. Desert oak is long-lived and widespread, occurring throughout central Australia where (in the absence of an intense bushfire) it can reach at least 100 years of age. It is often the only tree in a landscape dominated by spinifex, and can grow up to twelve metres in height, forming surprisingly dense stands. These shady groves, with their drooping green foliage and black stems, create a dramatic picture when intermixed with the contrasting red soil and the golden spinifex. Under clear blue skies it makes for one of the most memorable sights of outback travel. And to the traveller on a hot day, as lunchtime or evening approaches, the lure of a grove of desert oaks is almost irresistible.
Travellers on the Canning Stock Route in the Great Sandy Desert, unable to resist the lure of a grove of desert oaks (photo by Jack Bradshaw)
The climate of “desert oak country”, has been ironically described by that great explorer and bushman Len Beadell:
From November to March, it is searingly hot and dry; April, June and July have ideal temperatures, but it is dry. August and September are dry, and it appears to be fairly dry in October.
In this environment, desert oak is a tough survivor. Despite the searing heat of summer, frosty winter nights, recurring decade-long droughts and frequent sweeping bushfires, desert oak persists effortlessly. On one trip you might find a grove beneath whose shade you set up a pleasant camp. The next time you go through the same area the shady grove is gone, swept away in a fierce bushfire, but in a few years, they are back again, having enthusiastically and successfully regenerated.
They also have a wonderful ability to survive drought. This they do by simply shutting down, adopting a sort of hibernation. This is dramatically demonstrated in a pair of photographs in The Complete Guide to Central Australia by Jeff and Marie Carter. They contrast an oak in a good season, not long after rain, covered with a lush, almost tropical crown, with an oak in shutdown during a drought, the tree yellow and almost leafless (but still alive):
Like all the sheoaks, mature desert oaks lay a thick carpet of soft needles at their feet. This not only discourages the growth of other plants that might compete for moisture, but it also provides a soft bed on which a traveller can spread a swag at night, or take a post-prandial nap on a hot day.
In his wonderful book The Red Centre, the mammal collector and explorer H.H. Finlayson captures the essence of the desert oak. Writing about central Australia, he observed:
Of the larger trees of the sand areas, undoubtedly the most characteristic is the desert oak, the finest of all the casuarinas. It grows to a height of forty feet or more, usually in open groves destitute of any other growth save spinifex. In a melancholy way it is a most beautiful tree, with dark, drooping plumes of ‘foliage’ and a stem that appears jet black against the bare red sand.
Desert oak is especially beautiful on a moonlit night, as in this scene near Uluru, superbly captured by my friend Pat Fitzgerald:
The secret to the survival success of the desert oak in such a harsh climate is not just the capacity to shut down and endure when things are tough. It also has an astounding ability to capture and store moisture, and this in turn is thanks to its magnificent root system. The Aborigines knew all about this and desert oaks were an important survival resource for them. The tree bark is thick (protecting the tree from mild-intensity grass fires) and deeply fissured, and rain and dew settles in the cracks and hollows. In an 1893 report [see references] from a scientific expedition into the inland deserts there is a wonderful description of this process:
[The writer] ... described how an Aboriginal woman located and extracted water from a tree hollow. First she noticed a line of ants going up and down a tree, entering and emerging from a small knothole about shoulder-height from the ground. She then made a tube by removing the bark from a straight twig, using her teeth. Three or four of these tubes were then joined end to end and the long composite pipe was pushed through the hole in the knot and used as a drinking-straw to suck up the water trapped in the tree hollow. Where the opening to the water chamber was somewhat larger, an alternative procedure ... could be used; the Aborigine tied a bunch of grass to the end of a spear and dipped this into the water before pulling it out and squeezing the water out of the grass into a coolamon ... the tree species most exploited by Aborigines for tree-hollow water was the desert oak (Allocasuarina decaisneana) and such trees were as well known to the Aborigines of a region as were rock-holes (gnammas) and native soakage-wells.
Water is also stored in the shallow roots, and these were an additional and important resource. The root would be excavated with a digging stick and then held vertically above the mouth, allowing fresh water to drip out. It was not unusual to secure a "bucket-full" of water in this way.
But not every tree is a "water tree". Knowing which tree's roots to excavate was just as important a skill as the excavation itself. I have never tried it and would not like to have to rely on recognising a water tree, and then excavating its roots if I was doing a perish in some arid desert landscape.
There are many other elements to these stories. My forester-colleague Ian Kealley has explored the inland desert country with the traditional owners, and they described to him the "cultural significance of desert oaks (kurrkapi in their language) in that they represented deceased old people standing up in country". Other trees were pointed out to Ian as 'scar trees". These had had shields and other items cut from the trunks.
If there is one disappointing thing about the desert oak, it is the quality of the timber as firewood. Well, the relative quality anyway – by international standards it is right up there. Make no mistake, the desert oak has beautiful, typical sheoak timber, hard and durable and with an attractive grain. It was once used for making weapons, and today is turned into attractive ornaments, denser and tougher than the sheoaks of the coastal regions. But in the campfire it burns to a white ash and is not to be compared with the long-throbbing coals of a marble gum or mulgawood campfire.
Desert oaks, spinifex and rocky ranges - the essence of an inland Australian landscape (Photo by Andrew Burbidge)
But it is hard to complain about such a wonderful tree. As one anonymous writer put it:
When the wind blows across the outback plains, the desert oak’s shaggy foliage mutters with a subtle voice.
I know people who do not like the sound of the wind in a grove of sheoaks – the old bushmen always avoided them, it is said, because the sighing and keening reminded them of their womenfolk left at home. But I love that subtle voice and listen to it with pleasure.
With two colleagues Andy Burbidge and Tony Start, I once drove from Giles Weather Station to Alice Springs via Uluru, across the very heart of central Australia. At one point we diverged into the ranges to look for rock wallabies, and on a rough track, far from anywhere and in the middle of nowhere, I spotted a lone and sturdy desert oak. The lines from Thomas Gray’ s poem sprang to my mind:
… full many a flower is born to blush unseen
And waste its sweetness on the desert air ….
But no sweetness here was wasted on me. To my eyes this fine tree was a thing of beauty, an icon of the Australian inland, an image to stay upon the inward eye (“which is the bliss of solitude”) for a lifetime to come.
This story is based on a chapter in my book York Gum Chronicles – adventures with Western Australia’s most beautiful trees. Contact me by email (email@example.com) if you are interested in acquiring a copy.
Bayly A.E (1999): Review of how indigenous people managed for water in desert regions of Australia. Journal of the Royal Society of Western Australia, 82:17-25
Bonney, Neville (2016): Sheoaks – wind harps from desert to the sea. Neville Bonney, Tantanoola, South Australia
Carter, Jeff and Carter Marie (1989): The Complete Guide to Central Australia. Hodder and Stoughton, Sydney
Finlayson, H.H. (1935): The Red Centre. Angus and Robertson, Sydney